Project Summary/Abstract While a growing but still small number of studies corroborate that heat is associated with pediatric health impacts, this area of heat and child health remains critically understudied, thereby limiting public health prevention and clinical approaches focused on heat health risk reduction for children. Drawing on our preliminary work, we hypothesize that children vulnerability to the health effects of heat varies by age in ways that have important public health messaging consequences and that the greatest health impact to children from heat is among non-heat specific diagnoses and that outcomes such as injury and other diagnoses represent an important gap in existing research that is potentially missing the bulk of heat-associated health burden for children. We propose an investigation that uses an administrative dataset that is large enough to permit examination by smaller age categories and diagnostic subgroups to identify medically-fragile children and specific outcomes that will shed light on underlying etiology of the observed heat-health associations. Further, we employ a unique previously-compiled dataset of city-wide susceptibility indicators to understand community- level vulnerability to heat by chronic stressors. Aim 1: Develop and compare fine-grained, spatially and temporally-resolved calculations of heat across New York City (NYC). Aim 2: Determine which pediatric subpopulations in NYC are most susceptible to high ambient temperatures. Aim 3: Expand the pediatric health and heat analysis to the state level to understand the spectrum of risk across a gradient of urbanicity. Aim 4: Apply the child-health and heat association study findings to inform public health heat alert programs, state-specific heat vulnerability indices, and clinician awareness in NYS. Results of this research will be disseminated as part of the training and outreach series proposed in aim 4. Further, this research will help build infrastructure for assessing heat-risk reduction interventions.